I would be interested. I am an electrician by trade and I work with a lot of plumbers building hotels and other big buildings. everything that I got for my newest project has been found either as scrap getting thrown away or by trade for a liter or two. You wouldn't believe how many pieces of big copper get thrown away on my jobsites!
I have thought about this before and I was thinking about putting my extra supplies that I have on E bay and then sending the group an E-mail as to what I am willing to sell or trade.
I would be nervous about getting payment so using e bay / paypal would guarantee that We would get our money.
thank you for bringing up this Idea.